There are a number of standing/kneeling exercises in Pilates that might be good, but I would recommend checking with your PT to see if they are safe for you to do. A well-trained Pilates instructor will also have ideas as to how to work around your injury.

There is an exercise called chest expansion and another called thigh stretch (there is an upper back arch at the end of this one that you could leave out). These two would need to be done on equipment in a studio.

There are also arm exercises that you could do with light weights or with a Magic Circle. Even though they are arm exercises, you still initiate from your core, and as you gain strength you can increase resistance by using springs.

How is your balance? Any balance exercise should also have you thinking about that upper core as well.